The present invention relates to aromatic polycarbonates having chemically combined carbonate units derived from the polymerization of dihydroxy-meta-terphenyl. More particularly, the present invention relates to solvent resistant polycarbonate copolymers having chemically combined dihydroxy-meta-terphenyl carbonate units and carbonate units derived from a different biphenol such as bisphenol A.
Prior to the present invention, aromatic polycarbonates were often obtained by reacting 2,2-bis-(4-hydroxyphenyl)propane or "bisphenol A" and were utilized in a variety of applications requiring impact resistance. A preferred procedure for making polycarbonates, particularly polycarbonates having controlled molecular weight, is by the employment of a bisphenol bischloroformate, as shown by U.S. Pat. No. 4,973,664 which is incorporated herein by reference. Another procedure for making aromatic polycarbonates are shown by D. J. Brunelle, U.S. Pat. No. 4,363,905 employing bis(2-nitrophenyl)carbonate in solution with aromatic diols to effect a carbonate exchange reaction A third method is by treatment of aromatic diols with phosgene in the presence of an amine catalyst.
Although aromatic polycarbonates are often recognized for their high impact properties and transparent film forming characteristics, they often suffer from a lack of solvent resistance due to their solubility in a variety of organic solvents. It would be desirable therefore to provide film forming aromatic polycarbonates having improved solvent resistance.